Of great importance for the dyeing of hair are the so-called oxidation dyestuffs because of the intense and very fast dyes which they provide. These dyes are formed by the oxidative coupling of a developer component with a coupling component. The developers customarily used are nitrogenous bases such as p-phenylenediamine derivatives, diaminopyridines, 4-aminopyrazolone derivatives, or heterocyclic hydrazones. Useful as so-called coupling components are m-phenylenediamine derivatives, phenols, naphthols, resorcinol derivatives and pyrazolones. Compositions of this type are disclosed in application Ser. No. 526,232 filed on Nov. 22, 1974, by Rose et al., now U.S. Pat. No. 4,003,699, Jan. 18, 1977.
Good oxidation dyestuff components for the dyeing of hair should fulfill the following requirements.
They should develop the desired shades with sufficient intensity when oxidatively coupled with the respective developer component or coupling component, as the case may be. Furthermore, they have to possess an adequate capacity for being absorbed or adsorbed by human hair. In addition, they should be harmless from the toxicological and dermatological viewpoints.
It must form a tint of desirable hue of adequate intensity upon oxidative coupling with the opposite member of its pair. Furthermore, it must have an adequate to very good ability to be absorbed by human hair, and it should be harmless from the toxicological and dermatological viewpoints.
As developers, it is customary to use substituted or unsubstituted p-phenylenediamines for the purpose. However, this group of compounds has the disadvantage in many instances of causing skin sensitization and subsequent severe allergies in the persons to whom these compounds are applied. The developers which have been recently proposed for avoiding these dermatological disadvantages do not always give fully satisfactory technical results when applied.